Stephen Robertson, chief executive of the Big Issue Foundation, said it was "a terrifically generous act" and "a powerful statement from an artist".

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In Zao's case, this phenomenon is perhaps best understood as a self-statement: the artist's insistence on his personal and aesthetic identity in the face of the vagaries of borders and time.

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Today he launches a new exhibition by the artist Pablo Bronstein, his first curatorial statement of intent.

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Considerations include whether there is a verifiable chain of ownership for that work of art until today, whether that art work has ever been published in any exhibition catalogs or other publications, and whether it been appraised or received a statement of authenticity by a recognized authority on that artist.

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However, the museum at Majdanek, in south-eastern Poland, strongly condemned his statement and asked prosecutors to investigate, saying it was sure the artist had not obtained the ashes legally.

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"We mourn the passing of such an extraordinary and talented man, " said a statement from his wife Janet and his family, who were with the artist when he died Wednesday evening at New York-Presbyterian Hospital in Manhattan.

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